Vehicle-Mounted Network Device

Abstract

In order to correctly execute a control task in a FlexRay-based vehicle-mounted network system, data synchronization must be guaranteed by completing transmission/reception of all data within a communication cycle. The control task is called in synchronization with a communication cycle. Frames within a communication cycle are partitioned into a first-half slot group and a second-half slot group, each of which is a set of consecutive frames. During the slots of the first-half slot group, a data transmission/reception unit writes transmission frames of the second-half slot group and reads the reception frames of the second-half slot group. During the slots of the second-half slot group, the transmission/reception unit writes the transmission frames, and reads the reception frames, of the first-half slot group.

1 . A vehicle-mounted network device wherein a plurality of nodes are connected to a common network, each of said nodes includes a transmission buffer, a reception buffer, and communication control means, communication is performed in a fixed-period communication cycle, the communication cycle includes a plurality of slots each generated by dividing the communication cycle into a pre-specified communication time, and said communication control means uses a time division multiplex communication system that transmits and receives a frame, in which vehicle control data is included, via a pre-specified slot, wherein
 said communication control means performs transmission by reading from a transmission buffer and transmitting to a pre-specified slot and said communication control means performs reception by writing a frame in a pre-specified slot to a reception buffer,   said node has a control task and data transmission/reception means and said control task is called at a pre-specified time in a communication cycle to receive input data, to perform control, and to transmit output data and is executed in a control cycle that synchronizes with the communication cycle,   said data transmission/reception means receives input data by performing a pre-specified conversion for a frame in a pre-specified reception buffer to generate input data,   said data transmission/reception means transmits output data by performing a pre-specified conversion for output data to generate a frame and writing the frame into a pre-specified transmission buffer,   said plurality of slots are divided into two, a first-half slot group and a second-half slot group, each composed of a set of one or more consecutive slots, and   said data transmission/reception means performs transmission of output data corresponding to the first-half slot group of a certain communication cycle during a time allocated to the slots in the second-half slot group of the certain communication cycle and performs transmission of output data corresponding to the second-half slot group of the certain communication cycle during a time allocated the slots of the first-half slot group of a next communication cycle of the certain communication cycle.   
     
     
         2 . The vehicle-mounted network device according to  claim 1  wherein
 reception of input data corresponding to the first-half slots of the next communication cycle is performed during a time allocated to the second-half slots of the certain communication cycle and 
 reception of input data corresponding to the second-half slot group of the certain communication cycle is performed during a time allocated to the first-half slots of the certain communication cycle. 
 
     
     
         3 . A vehicle-mounted network device, wherein
 a plurality of nodes are connected to a common network, each of said node includes a transmission buffer, a reception buffer, and communication control means,   communication in said network is performed in a fixed-period communication cycle,   the communication cycle includes a plurality of slots each generated by dividing the communication cycle into a pre-specified communication time, and   said communication control means uses a time division multiplex communication system that transmits and receives a frame, in which vehicle control data is included, via a pre-specified slot, wherein   said communication control means performs transmission by reading from a transmission buffer and transmitting to a pre-specified slot and said communication control means performs reception by writing a frame in a pre-specified slot to a reception buffer,   said node has a control task and data transmission/reception means,   said control task is called at a pre-specified time in a communication cycle to receive input data, to perform control, and to transmit output data and is executed in a control cycle that synchronizes with the communication cycle,   said data transmission/reception means receives input data by performing a pre-specified conversion for a frame in a pre-specified reception buffer to generate input data,   said data transmission/reception means transmits output data by performing a pre-specified conversion for output data to generate a frame and writing the frame into a pre-specified transmission buffer,   the communication cycle has an idle time during which no frame is transmitted/received from a time in the communication cycle to the end time of the communication cycle or in which there is no slot in the idle time,   the control task execution time is in a range other than the idle time and the start time of the control task is set so that the execution time of the control task does not extend across the communication cycle, and   the data transmission/reception means writes all output data, generated by the control task in a certain communication cycle, to a transmission buffer during the idle time of the certain communication cycle and said communication control means transmits the output data in a next communication cycle of the certain communication cycle.   
     
     
         4 . The vehicle-mounted network device according to  claim 3  wherein
 in the idle time, said data transmission/reception means receives all input data, which will be used in the next communication cycle, in the certain communication cycle.